GMAC_NITER:1,2,4,8,16
GMAC_ROLL_THRESHOLD:2,4,8,16
GMAC_BLOCK_SIZE:4096,131072,2097152,8388608
GMAC_STENCIL_DIM_ELEMS:256,320,384
GMAC_MEMCPY_TYPE:1,2,3
GMAC_MEMCPY_GMAC:0,1
GMAC_XSIZE:
